US officials held a preliminary meeting with representatives of the Haqqani network, a group Washington has blamed for a series of attacks in Afghanistan, Hillary Clinton, the US secretary of state, said during a visit to Pakistan.

Clinton was in Islamabad on Friday to discuss joint efforts against the Taliban and the Haqqani network, and was asked at a journalist roundtable about reports that US officials had met with Haqqani representatives directly.

"We have reached out to the Taliban, we have reached out to the Haqqani network to test their willingness and their sincerity, and we are now working among us - Afghanistan, Pakistan and the United States - to try to put together a process that would sequence us toward an actual negotiation," Clinton said.

No negotiations are under way, she said.

A senior US official said later that the meeting took place in the summer, before September's attack on the US embassy in Kabul that US officials have linked to the Haqqanis.

'Double game'

They said the meeting had been organised by Pakistan's powerful spy agency, the Inter-Services Intelligence (ISI), which US officials have repeatedly charged with playing a "double game" with armed groups and working with the Haqqanis.

"Pakistani government officials helped to facilitate such a meeting," Clinton said.

The US Treasury last month imposed sanctions on individuals it said were linked to the Haqqani network, but stopped short of putting the group on an official blacklist of terrorist groups, which would bar any official contact.

"We had one preliminary meeting to essentially just see if they would show up for even a preliminary meeting," Clinton said.

The US official described the Haqqani meeting as one of a number of "straws in the wind" that the US is pursuing as it seeks to set the framework for an eventual political settlement in Afghanistan.

Clinton, who met Yousuf Raza Gilani, the Pakistani prime minister, on Thursday, also called on Pakistan to crack down on armed groups it says are operating in Afghanistan from bases inside Pakistani territory, or face unilateral action by the US.

Since abandoning Afghanistan's Taliban in 2001 and joining the US-led "war on terror", Pakistan has received billions in US military and civilian aid.

But ties between Washington and Islamabad have soured in recent months, notably since the March raid by US forces in which Osama bin Laden, the leader of al-Qaeda, was killed in Abbottabad.

'Give and take'

However, despite the apparent frustrations, the two countries could not give up their relationship, Clinton said, describing a "strong" Pakistan as being critical to regional stability.

"There is frustration on both sides, which I recognise," Clinton said, calling for "give and take" from both sides.

"We look to Pakistan to take strong steps to deny Afghan insurgents safehavens and to encourage the Taliban to enter negotiations in good faith," she said.

"Now we have to turn our attention here on the Pakistani Taliban, the Afghan Taliban, Haqqani and other terrorist groups and try to get them into a peace process but, if that failed, prevent them from committing more violence and murdering more innocent people."